As wildfires rage across parts of Canada, one fire in particular highlights concerns about so-called “zombie fires.”
Authorities in the Northwest Territories are monitoring a large fire that broke out after lying dormant underground for the winter months.
Fires that linger through winter in Canada were once considered a rare phenomenon, but experts warn these events are becoming more common as temperatures get warmer and less snow falls.
According to the BC Forest Fire ServiceA “zombie fire,” more commonly known as a winter fire or remnant fire, occurs when a wildfire that burned underground the previous year has continued to smolder all winter.
The agency warns that these “residual hot spots” may resurface with the onset of warmer, drier weather in the spring.
Jennifer Baltzer, associate professor of biology at Wilfrid Laurier University and Canada Research Chair in Forests and Global Change, told CTVNews.ca in a phone interview Monday “zombie fires” that burn in biomass, such as roots and bowls. of trees or in peat soils, of the affected landscape.
Such events can cause wildfire season to start earlier than expected and last longer, he said. Baltzer added that overwintering fires also have the potential to cause much greater ecosystem change and carbon loss than a typical wildfire.
“A single-season fire burns through the season and then ends, whereas a smoldering fire continues to burn wood and peat soils throughout the winter, very, very slowly, but we continue to see combustion throughout the winter,” Baltzer said.
According to a 2021 studyOverwintering fires generally accounted for a small amount (about one percent) of the total area burned in the Northwest Territories and Alaska between 2022 and 2018.
However, researchers from the University of Amsterdam and the University of Alaska Fairbanks found that there was a “surprising” increase in the number of fires that hibernated in individual years.
In Alaska, for example, winter fires accounted for 38 percent of the landscape burned during the 2008 wildfire season, according to the study.
Experts suggest that “zombie fires” could become more common due to climate change, as the hot, dry conditions associated with intense fire years can trigger this deep burning of carbon-rich biomass.
A study published in 2019 found that rising summer temperatures associated with climate warming may promote future winter fire survival, threatening boreal regions, including the subarctic, arctic, Northwest Territories, and northern areas in Ontario , Alberta and Saskatchewan.
Baltzer, who is leading a team of researchers collecting field data on “zombie fires” in the Northwest Territories, hopes to further analyze how these fires affect carbon loss and forest regeneration in Canada.
Baltzer explained that shrubs that quickly bounce back from wildfires can do so thanks to subterranean plant systems. However, “zombie fires” damage these systems, as well as tree seedlings, which “inhibits reproduction and recolonization of these sites” after the fire, she said.
“This is a concern because of changing fire activity in boreal forests,” Baltzer said. “High-latitude systems are warming three to four times faster than the planet… And this really fast warming is making these systems more flammable… [resulting in] larger areas burned, more severe fires and more frequent fires.”
Baltzer said the overwintering fires are “inherently linked to climate change” as they become more frequent after years of increased wildfire activity, which is steadily increasing amid global warming.
With this in mind, Baltzer said preventing “zombie fires” will require a reduction in fossil fuel emissions to curb the overall production of greenhouse gases that drive global warming.
While Baltzer acknowledges this requires a global effort and is beyond the scope of his research team, he says they are working to provide fire managers with information to support a better understanding of where “zombie fires” are in Canada so help inform understanding of the behavior of these fires and how to respond.
See map showing wildfires burning in North America, provided by ESRI Canada, full screen
With archives from The Canadian Press